CN8237EBGB Mindspeed Technologies, CN8237EBGB Datasheet - Page 179

• Manufacturer Part Number: CN8237EBGB
• Description: ATM SAR 622Mbps 3.3V ABR/CBR/GFR/UBR/VBR 456-Pin BGA
• Manufacturer: Mindspeed Technologies

Specifications of CN8237EBGB

• Package: 456BGA
• Traffic Class: ABR|CBR|GFR|UBR|VBR
• Utopia Type: Level 1|Level 2
• Host Interface: PCI
• Maximum Data Rate: 622 Mbps
• Typical Operating Supply Voltage: 3.3 V
• Minimum Operating Supply Voltage: 3.135 V

CN8237
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
6.2.8 PCR Control for Priority Queues
28237-DSH-001-C
mechanism to trigger an increase in the scheduling priority by one priority level,
if the transmit rate on that channel falls below its specified MCR. This is done
using the MCRLIM_IDX field in that VCC’s SCH_STATE entry in the SEG
VCC table entry. MCRLIM_IDX is an 8-bit index into a table containing
256 entries (each formatted as described in
limit values, and each indicating a trigger point for an increase in the VCC’s
priority for that scheduled slot.
user can accomplish this by setting each of the values in the GFR MCR Limit
bucket table entries as follows:
An additional level of traffic shaping can be established on GFR-UBR priority
queues by shaping to a specified PCR. (See
The CN8237 provides an optional method of creating tunnels (that is, limiting the
bandwidth of a group of channels), by allowing the user to assign a PCR to a
scheduling priority queue so that the aggregate of the rates of the channels
assigned to that priority queue are not greater than the PCR assigned. This can be
done for UBR, VBR, ABR, and UBR-GFR traffic classes.
line rate. The queues to be shaped are identified using the QPCR_ENAx bits in
the SCH_PRI and SCH_PRI_2 registers. The associated PCR for each queue thus
enabled is specified in one of the two PCR_QUE_INTxx registers. These PCR
values are stored as schedule table intervals. QPCR_INT3 maps to the highest
priority queue that is enabled for PCR shaping, QPCR_INT2 to the next highest
priority PCR shaped queue, and so on. If only one priority queue is enabled for
PCR shaping, it is shaped using the QPCR_INT3 value.
QPCR_INT2 are used, and so on.
The CN8237 helps guarantee MCR on a GFR channel by providing a
To disable this priority bumping, set MCR_LIMIT to its maximum value. The
1.
2.
3.
A maximum of 4 of the 16 priority queues can be shaped to a PCR less than
If two priority queues are enabled for PCR shaping, QPCR_INT3 and
Set NONZERO bits to 1.
Set MCR_EXP fields to decimal value of 31 (that is, all-1s).
Set MCR_MAN fields to decimal value of 511 (that is, all-1s).
Mindspeed Technologies
™
6.2 xBR Cell Scheduler Functional Description
Table
Section
6-18), each containing MCR
6.2.8.)
6.0 Traffic Management
6-23